This invention relates generally to apparatus for measuring the elevations of land structures and the like, for the use of architects, builders, engineers, surveyors, construction workers, farmers and other persons whose jobs require an accurate elevaton-indicating instrument at a reasonable cost.
The invention is particularly directed to an elevation indicator which makes use of liquid and comprises a reservoir for containing the liquid and supported at a base elevation, a staff provided with a scale and clear tube, extending along the scale, and a flexible tube extending from the reservoir to the clear tube on the staff. Liquid flows from the reservoir to the clear tube through the flexible tube, so that the water level in the clear tube is the same as the water level in the reservoir. The liquid level in the clear tube is defined by the meniscus. The top of the reservoir and the top of the clear tube are generally vented to prevent an air lock at either end of the system and to allow the meniscus in the clear tube to move freely relative to the clear tube as it maintains the same level as the level of liquid in the reservoir.
One difficulty encountered with prior art devices is that elevation readings and settings are generally difficult to obtain because the devices only give a level point. In most cases, a measurement must then be subtracted or added in order to obtain an elevation measurement between two different points. However, in the case of levels in which the clear tube is moved relative to the staff, readings are difficult to obtain because of the bouncing of the meniscus as it is moved vertically. The device cannot be read accurately until the meniscus is allowed to settle down after movement. In at least one case where a scale was used on the staff, it was necessary to use a non-standard, calibrated scale. In addition, all of these solutions add greatly to the cost and complexity of the indicator. These and other difficulties experienced with the prior art elevation indicators have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide an elevation indicator which is reliable and easy to use.
Another object of this invention is the provision of an elevation indicator in which the meniscus in the clear tube on the measuring staff moves freely, so that it reaches the level of the reservoir quickly and accurately without danger of loosing fluid from the system.
A further object of the present invention is the provision of an elevation indicator, in which elevation readings can be taken directly from the scale on the measuring staff.
It is another object of the instant invention to provide an elevation indicator, in which the measuring staff has an adjustable scale which is easy to use, and which maintains its accuracy over an extended period of use.
A still further object of the invention is the provision of an elevation indicator capable of measuring a greatly increased range of elevation, without changing the location of the reservoir.
It is a further object of the invention to provide an elevation indicator, having a support for the reservoir which also functions as a carrying case for various elements of the indicator.
It is a still further object of the invention to provide an elevation indicator which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service with a minimum of maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.